FREEOAB Study for Overactive Bladder: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for FREEOAB Study for Overactive Bladder (NCT04547920), a na na study. The primary outcome is Percentage of Responders in Voiding (Urinary Frequency) Events.

2. Clinical Question

The study, titled FREEOAB, is described as a prospective, multicenter evaluation of a wearable neuromodulation system for overactive bladder symptom control. Its listed primary outcome concerns urinary frequency rather than a broad measure of every overactive bladder symptom. The endpoint is based on the number of voids per day and compares the baseline assessment with Week 12.

The registry also lists secondary outcomes for response in incontinence events, response in urgency events, and overall response rates at 12 Weeks and 12 Months. Those listings indicate additional questions considered by the study record, but the result values for these outcomes are not reported in the registry record. The primary responder result is also not reported in the registry record, so the efficacy question cannot be answered from the posted information alone.

The record describes an initial 12-week period and an optional continuation for qualifying participants who elected to continue. That extension is not a randomized comparator. Without a separate control group, the study can describe outcomes among participants receiving the device, but the registry record does not establish how those outcomes compare with what would have occurred under another treatment or no treatment.

3. Trial Design

FREEOAB is described as a prospective, multicenter study of a wearable system for overactive bladder symptom control. The registry lists the study as completed and reports enrollment of 96. The listed intervention is a wearable bladder modulation system. The study design is sequential, allocation is recorded as not applicable, and masking is listed as none. These entries do not describe a randomized, masked comparison between treatment groups.

The group description specifies an initial 12 Weeks of therapy using wearable, closed-loop, continuous-sensing tibial nerve stimulation. It also describes an optional continuation for Months 4–12: participants who qualified and chose to enroll signed new informed consent and continued therapy sessions. The registry does not report the number who qualified, elected to continue, or completed follow-up. It therefore does not support an assessment of how representative the continuation participants were of the original study group.

The primary outcome is assessed at 12 Weeks. Its stated population is participants with a reported baseline voiding symptom, defined in the registry as an average of > 8 voids per day. The response definition uses change from baseline to Week 12. The registry record does not report the number of participants included in this endpoint analysis, how missing Week 12 assessments were handled, or whether the analysis population differed from the enrolled group.

The record lists five outcome measures and names secondary response outcomes for incontinence events, urgency events, and overall response at 12 Weeks and 12 Months. It reports no analysis records. The study start date is 2021-01-11, and primary completion is recorded as 2021-10-08. The registry does not report a detailed statistical analysis plan, the rationale for the enrollment target, or interim-analysis procedures. Those design details should not be inferred from the study type or the recorded enrollment.

Because there is no stated control group, the study design is suited to describing outcomes observed during use of the system, not to isolating the effect of the device from other influences. Changes over time could reflect multiple factors, and the registry record does not provide a comparison that would distinguish among them.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Initial 12-Week Study

Optional 12-Month Long Term Follow-Up

Analysis population for the primary outcome, as defined in the registry: Number of Subjects with Reported Voiding Symptom (Avg \> 8 / day) at Baseline

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Responders in Voiding (Urinary Frequency) Events, measured over 12 Weeks.

The primary endpoint is the percentage of responders in voiding, or urinary frequency, events at 12 Weeks. The registry defines a responder as a participant who either achieves a 50% or greater reduction, from baseline to Week 12, in total voids per day relative to an upper normal limit of 8 voids per day, or returns to normal, defined as 8 or fewer voids per day at Week 12. The endpoint population is described as participants with an average of > 8 voids per day at baseline.

This is a binary participant-level outcome: each participant either meets the stated response definition or does not. The endpoint combines two pathways to response—meeting the reduction criterion or reaching the stated normal range. A responder percentage can be easier to interpret than an average change alone because it expresses the share meeting a prespecified threshold. However, it does not show how far each participant’s result changed, nor does it describe the distribution of changes among responders or nonresponders.

The threshold is intended to distinguish a meaningful category of change under the registry’s definition. It is not, by itself, proof that participants experienced a particular degree of benefit in daily life. The record does not report the observed responder count or percentage, an uncertainty interval, or the number included in the endpoint analysis. Thus, the endpoint’s definition is available, but its observed result and precision are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is binary at the participant level: a participant is classified as a responder or not according to the stated rule. For this kind of endpoint, the basic descriptive result is the number meeting the rule and the percentage among participants included in the analysis. The registry record gives the rule but does not report those result values or the analysis denominator.

What does the response rule capture?

The rule offers two routes to response: a 50% or greater reduction, from baseline to Week 12, in total voids per day relative to an upper normal limit of 8, or a Week 12 level of 8 or fewer voids per day. It therefore classifies participants using a threshold rather than reporting every participant’s change as a continuous measurement. General statistical explanation: thresholds can make results easier to communicate, but they also discard information about how close a participant was to the cutoff and how large a change occurred beyond it. Two participants who both meet the threshold may have quite different changes.

The endpoint is defined for participants whose baseline average was > 8 voids per day. That restriction is part of the endpoint population, not necessarily a description of everyone enrolled. A clear report would distinguish enrollment from the number meeting the baseline criterion and the number included at Week 12. Those counts and the handling of missing observations are not reported in the registry record.

How should uncertainty be considered?

A confidence interval is a range of values compatible with the observed data under a specified statistical method. General statistical explanation: for a responder percentage, an interval helps show the precision of the estimate; a wider interval indicates greater uncertainty, while a narrower interval indicates greater precision. The registry record does not report a confidence interval for the primary outcome, and without the observed responder count and analysis denominator one cannot assess its precision from the record.

A hypothesis test, when used, evaluates data against a stated null hypothesis and relies on a specified analysis plan. A p-value alone would not measure the size or practical importance of a response. The record reports no analysis records and does not state a primary-outcome hypothesis test or statistical plan. No test result should be inferred from the endpoint definition or study completion status.

Why does the design affect interpretation?

The registry describes one study group and no randomized comparator. General statistical explanation: random allocation to a control group can help balance measured and unmeasured factors, on average, and supports a direct between-group comparison. A single-group before-and-after assessment does not provide that protection. The registry record can describe measured outcomes over time, but it cannot establish from a control comparison whether any change was caused by the intervention.

The design is sequential, and the continuation from Months 4–12 was optional for qualifying participants who chose to enroll. General statistical explanation: when continued observation depends on eligibility and participant choice, the longer-term group may be selected rather than representative of everyone who began the study. The record does not report continuation counts or results, so it is not possible to characterize that selection or assess long-term outcomes.

What do the safety counts mean?

The registry reports serious adverse events as counts among participants at risk, and separately reports counts in an other-event category. Such counts describe what was recorded during the study; they do not by themselves compare risk with another treatment. General statistical explanation: interpreting adverse-event frequency also depends on clear event definitions, observation time, and complete reporting. The registry record does not list serious-event terms or describe the other events, and the recorded counts do not establish the absence of unrecorded events.

The posted sample-size assumptions describe an illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the stated effect to detect is a fraction of the observed effect. The record does not report the observed primary effect or sample-size illustration values in the information available for this analysis. Such planning illustrations are conditional calculations, not observed power and not evidence that the original design used those assumptions. The study itself is not described as a two-arm randomized comparison.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("12 Weeks Followed by Optional 12 Month Continuatio")
n      <- c(89)
events <- c(55)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  12 Weeks Followed by Optional 12 Month Continuatio  89  55  61.8  50.9  71.9  51.4  71.2  51.4  71.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists several outcomes: response in voiding frequency as the primary endpoint, and secondary outcomes for incontinence events, urgency events, and overall response at 12 Weeks and 12 Months. Considering several outcomes raises a general statistical issue called multiplicity. When many outcomes or analyses are tested, the chance of at least one apparently notable result can increase unless the analysis plan accounts for the number and relationship of tests. The registry record does not report a multiplicity strategy, such as an ordering of tests or an adjustment to account for multiple comparisons.

The record lists five outcome measures, but reports no analysis records. It does not state which outcomes were formally tested, whether any analyses were prespecified, or whether subgroup analyses were planned. Those details are not reported in the registry record; their absence should not be interpreted as evidence that a particular method was or was not used outside the record.

Missing-data handling is also not reported. The registry does not state how many participants had baseline and Week 12 assessments for the primary endpoint, how missing outcome measurements were treated, or whether participants with incomplete data were counted as nonresponders. These choices can affect both the estimated responder percentage and its uncertainty. Without them, the analysis population and the consequences of missing observations cannot be assessed.

The primary endpoint population is described by a baseline symptom criterion, but the number meeting that criterion is not reported. The record also does not provide a detailed definition of the analysis population, the treatment of withdrawals, or the number included in the optional continuation. These are important for understanding which participants the results would represent. Since the efficacy results themselves are not reported in the registry record, neither multiplicity nor missing-data effects can be evaluated from observed estimates.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The safety record lists no serious adverse events among 96 participants at risk. It separately lists 17 participants with an event in the registry’s other-event category among 96 at risk, and reports no deaths. These are counts as recorded, not comparative estimates. The study record does not describe a separate control group against which to compare them.

No serious adverse-event terms are listed. The registry record also does not provide descriptions of the 17 other events, their severity, timing, duration, or relationship to the device. The phrase “other-event category” should therefore be read as a registry category, not as a detailed clinical characterization. The record does not give information about how long each participant was observed for safety outcomes.

General statistical explanation: a count of zero recorded serious events does not prove that an event cannot occur; the interpretation depends on the amount and completeness of observation and on how events were defined and collected. Similarly, a count in an event category does not by itself indicate the event rate relative to another option. The posted safety figures are useful as a description of what the registry reports, but they do not support a full comparative safety assessment.

13. What the Result Does, and Does Not, Mean

The registry record describes a prospective study of a wearable system and defines a participant-level urinary-frequency response at 12 Weeks. It also reports enrollment and limited safety counts. These features show what the study set out to examine and what safety information was recorded, but the primary efficacy result is not reported in the registry record.

Without the observed responder count or percentage, the primary outcome cannot be characterized as frequent or infrequent. Without an uncertainty interval or other analysis estimate, its precision cannot be assessed. Enrollment alone does not fill that gap: the primary endpoint applies to participants meeting a baseline voiding-frequency criterion, and the number meeting that criterion or included in the Week 12 analysis is not reported.

The single-group design also sets a limit on causal interpretation. Even if a before-and-after change were reported, a comparison with baseline alone would not show what would have happened over the same period without the wearable system. The registry record does not include a randomized control group to support that comparison. It therefore does not establish a treatment effect relative to an alternative or no intervention.

The optional continuation is another distinct question. It involved qualifying participants who elected to continue, and the registry record does not report how many continued or what their longer-term outcomes were. It cannot be assumed that those participants represent all who entered the initial study.

The reported safety counts document no serious adverse events and 17 participants in the other-event category, with no deaths recorded. They do not provide event descriptions or a comparative safety estimate. Taken together, the posted information supports a description of the study’s design, endpoint definition, and recorded safety counts. It does not support a conclusion about the magnitude, precision, or cause of an efficacy response, nor a complete assessment of safety.

14. Why This Trial Matters Statistically

This study illustrates why endpoint definitions and endpoint results need to be read together. The registry gives a specific rule for classifying a urinary-frequency response, including the baseline population to which it applies. That clarity helps identify the intended clinical measurement. But a definition alone is not a result: without the observed responder count, percentage, analysis denominator, and uncertainty, the endpoint cannot answer how often participants met the rule.

It also illustrates the difference between describing change and estimating a comparative effect. The study is prospective and evaluates a device during use, but no control group is described. General statistical principle: a prospective design can organize measurement over time, while randomization and a comparator address a different question—whether outcomes differ from those under another condition. Those design features should not be conflated.

The optional continuation highlights a further issue in longer-term follow-up. Eligibility and willingness to continue can shape who contributes later observations. Without continuation counts and results, long-term outcomes cannot be interpreted from this registry record. The same applies to missing-data methods: knowing the endpoint and enrollment is not enough to know which participants contributed to an estimate.

Finally, the safety figures show why counts need context. A zero count for serious adverse events is informative as a registry observation, but it is not proof of zero risk; the event terms, observation details, and comparator are absent. In statistical reading, the design, population, endpoint, denominator, uncertainty, and reporting completeness all shape what a result can establish. Here, the endpoint and design are described, while the primary efficacy estimate and several details needed for interpretation are not reported in the registry record.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The main limitation for interpreting efficacy is that the registry record does not report the primary responder result. It gives the definition and time point, but not the responder count, percentage, analysis denominator, confidence interval, or test result. The listed enrollment of 96 cannot be treated as the number analyzed for the primary endpoint because the endpoint population is restricted by baseline voiding frequency and the analysis count is not reported.

The design is sequential, with no randomized comparator described and masking listed as none. Consequently, the record does not support a like-for-like comparison or a causal estimate against another treatment. The record also does not report a detailed analysis plan, sample-size justification, interim-analysis procedures, or the method used to handle missing data. These details should not be inferred from the design label or enrollment.

Longer-term interpretation is limited by the optional continuation. Participants needed to qualify and elect to continue, while the record does not report the number continuing or their outcome results. This leaves both the extent of selection and the long-term response uncharacterized.

The registry lists secondary outcomes but does not report their results or a multiplicity approach. It also gives no analysis records. The safety record lacks serious-event terms and details about the events in its other-event category, as well as information about observation duration. These gaps constrain interpretation of both efficacy and safety. They are limitations of what is reported in the registry record and do not establish what may have been measured or analyzed outside it.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: FREEOAB Study for Overactive Bladder — NCT04547920.
• Registry record last updated 2025-02-26; status last verified 2025-02.
• Results first posted 2025-02-26.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

FREEOAB is a completed prospective, multicenter study of a wearable bladder-modulation system for overactive bladder. The registry reports enrollment of 96, a sequential design, no masking, and an initial 12-week treatment period with an optional continuation for qualifying participants who chose to enroll.

The primary outcome is the percentage of participants meeting a defined urinary-frequency response at 12 Weeks, among participants with an average of > 8 voids per day at baseline. The registry record does not report the primary outcome result, its analysis denominator, or an uncertainty estimate. Secondary outcomes are listed, but their results are not reported.

For safety, the record reports no serious adverse events among 96 at risk, 17 participants with an event in the other-event category among 96 at risk, and no deaths. Serious-event terms are not listed, and details of other events are not reported. The absence of a described control group limits comparative interpretation of both efficacy and safety.